In the United States, what circuit does black wire insulation indicate in a three-wire 120 V cable?

In standard United States residential AC wiring, specific colors are used to safely identify the function of each wire. The black wire (and sometimes red in multi-phase circuits) is the 'hot' wire, meaning it carries the dangerous voltage from the breaker panel to the device. It is critical not to confuse AC wiring colors with standard DC wiring colors often found in electronics or automotive systems. In low-voltage DC circuits, black is typically used for the negative or ground connection, whereas red is positive. In US AC house wiring, white is neutral and green or bare copper is the equipment ground.